• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 3
  • Tagged with
  • 83
  • 40
  • 35
  • 35
  • 28
  • 28
  • 9
  • 8
  • 8
  • 8
  • 8
  • 7
  • 5
  • 5
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

The use of the complex summation method for formulating algorithms for decoupling vertical/horizontal motions of rolling aircraft

Belo, Eduardo Morgado January 1987 (has links)
No description available.
62

An experimental study of sonic and supersonic nozzles and their application to high pressure ejectors for aircraft attitude control

Miller, P. January 1988 (has links)
A study has been conducted of reaction controls for VSTOL aircraft using thrust augmenting ejector techniques. Rapid mixing nozzles have been developed for high pressure ejectors. Mass flow increases for sonic nozzles of up to 50\ at x/D=8 were recorded, compared with plain circular nozzles. Their use was found to improve the thrust performance of a simple ejector by 9\, and larger increases are believed possible. Results from an ejector performance prediction model were successfully compared with experimental data. The use of rapid mixing nozzles in a practical ejector design has been assessed. It is predicted that a maximum thrust increment of 20\ ·could be achieved, compared with a simple fully expanded jet flow.
63

Reconfigurable integrated modular avionics

Omiecinski, Tomasz Adam January 1999 (has links)
Integrated Modular Avionics standardises hardware and software platforms of Line Replaceable Modules (LRMs) and other system components in order to reduce the overall cost of system development. operation and maintenance. Several identical processing units within a cabinet. and fast communication media in the form of a backplane bus introduces further possibility of reconfiguring the system in terms of changing the applications performed by particular core LRMs. In this thesis a study into Reconfigurable Integrated Modular Avionics is presented. The main objectives of the project were to investigate the benefits, and feasibility of, employing autonomous dynamic in-tlight reconfiguration of the system as a means for providing fault-tolerance. In this approach, allowing processing modules to change their function permits the system to share the redundant modules as well as sacrificing less important avionics functions to sustain the more critical applications. Various architecture examples are reviewed in order to establish a system design that would support reconfiguration at a minimal cost. Two modified ARINC 651 architecture examples are proposed for implementation of dynamic in-flight reconfiguration. The benefits of reconfiguration are identified with the use of Markov state space analysis, and are found to be substantial with respect to the reduced number of redundant processing modules required to implement the system functions within the safety requirements. Suitable reconfiguration schemes are identified, and the most promising one is formally specified with the use of the Vienna Development Method. The safety properties of the scheme are shown based on the specification. In order to study the feasibility of autonomous dynamic reconfiguration, the scheme is implemented into two distinct systems, and the results of the practical observation of the system behaviour are presented and discussed. As the project was sponsored by the UK Civil Aviation Authority, a number of certification issues related to reconfigurable avionics systems are identified and discussed based on the practical implementation and previous theoretical analysis. It is concluded that dynamic in-flight reconfiguration of avionics systems can lead to substantial savings in terms of the reduced number of required core LRMs, and greater fault-tolerance than traditional non-reconfigurable systems
64

Analytical redundancy scheme for improving reliability of automatic flight control systems for aircraft

Alkhatib, K. Y. January 1985 (has links)
Any redundancy scheme in aircraft control systems is usually considered separately from the control algorithms involved. All feedback control systems are usually designed under the assumption that their sensors will not fail. When the integrity requirements demand it, then a redundancy scheme must be designed to provide any required measurements with only extremely short interruptions to normal service being caused by failures of individual sensors.
65

Design of tracking systems incorporating multivariable plants

Yamane, Hideaki January 1991 (has links)
The methodology for the design of error-actuated digital set-point tracking controllers proposed by Porter and co-workers has emerged as a result of the pursuit of effective and practical solutions to the problem of designing digital control systems for unknown, dynamically complex multivariable plants with measurable outputs. In this thesis, such digital set-point tracking controllers and the resulting digital set-point tracking systems are enriched to embrace plants with unmeasurable outputs and plants with more outputs than manipulated inputs. In the study of the latter plants, the novel concepts of limit tracking (i.e. the tracking exhibited by plants with more outputs than inputs) is introduced and an associated methodology for the design of self-selecting controllers is proposed. Such controllers involve the selection of different set-point tracking controllers to control the most critical subset of plant outputs based upon the developed rigorous theoretical foundations for the limit-tracking systems. In such foundations, the classification of linear multivariable plants into Class I and Class II plants based upon their steady-state transfer function matrices facilitates the assessment of the feasibility of limit-tracking systems. Furthermore, the associated order-reduction technique simplifies the problem of deciding the minimum numbers of different subsets of plant outputs to be controlled by corresponding set-point tracking controllers. In addition, the dynamical properties of limit-tracking systems are also investigated using the phase-plane method and a methodology for the design of supervisory self-selecting controllers is proposed so as to prevent the occurrence of dynamical peculiarities such as limit-cycle oscillations which might happen in limit-tracking systems. The effectiveness of all the proposed methodologies and techniques is illustrated by examples, and the robustness properties of set-point tracking systems and limit-tracking systems in the face of plant variations and unknown disturbances are tested. Finally, self-selecting controllers are designed for a nonlinear gas-turbine engine and their practical effectiveness is clearly demonstrated.
66

The application of nonlinear control theory to robust helicopter flight control

Maharaj, Davendra Yukteshwar January 1994 (has links)
No description available.
67

Design of a microprocessor-controlled shear warning device for general aviation aircraft

Samaka, Muhammad B. January 1984 (has links)
Wind-shear is a spatial or temporal gradient in wind speed and/or direction, and is generally associated with the presence of cold and warm fronts and thunderstorm cells. It is a serious hazard in the terminal stages of flight for all aircraft but for light aircraft in particular. The research work presented in this dissertation concerns the design of a wind-shear detection system which involved the application of estimation theory and digital simulation techniques. The wind-shear detection system was designed after a careful study of the results obtained from a digital simulation of an aircraft landing phase, including the effects of wind-shear.
68

The characterisation, modelling and detection of series arc faults in aircraft electrical power distribution systems featuring solid state power controllers (SSPCs)

Handy, Peter James January 2016 (has links)
Electrical power demand in aircraft has grown significantly over the last century, and this trend continues with the More Electric Aircraft (MEA) and All Electric Aircraft (AEA) concepts. Higher voltages such as 270VDC are required to deliver additional power to loads and to optimise aircraft mass. Increased voltages inflict more stress on the Electrical Wiring Interconnect System (EWIS) and increase the impact of series arc faults caused by wiring defects. Solid State Power Controllers (SSPCs) are used to provide fast protection in high voltage distribution systems. The aim of this work is the characterisation, modelling, simulation and detection of series arc faults in 28VDC and 270VDC electrical power distribution systems featuring SSPCs. The majority of passive detection schemes in the literature were designed based on empirical data rather than well characterised electric arc parameters, and thus nuisance trips are unavoidable. To address this series arc faults in 28VDC and 270VDC solid state power distribution systems were characterised using the SAE5692 "Loose terminal" method [8], and it was found that 270VDC arc faults cause a minimal ~5.6% reduction in loop current and load voltage compared with ~54% in 28VDC systems. SSPC output voltage transients caused by series arcs were found to be limited by the presence of SSPC snubbers. Increasing the system loop inductance was found to improve series arc stability resulting in fewer arc quench events. Increasing the capacitive load reduces arc stability and causes arcs to quench more readily thus simplifying detection. These results were later used to experimentally validate a novel series arc fault SPICE model based on the static Nottingham V-I model [9] and wider solid state electrical system model. The arc current and SSPC output voltage results were also used to create a prototype passive series arc fault detection system, which has been demonstrated to SAE5692 under laboratory conditions [8]. A novel multilayer PCB current sensor was developed and experimentally validated for this prototype. To further reduce nuisance trips an innovative active arc fault perturbation scheme was simulated and experimentally demonstrated using SSPC modulation to stimulate and detect arc quench. Another novel complementary series arc fault prevention / confirmation scheme was simulated and experimentally validated using SSPC leakage currents. To minimise nuisance trips due to manufacturing and installation errors a unique Built-In Test (BIT) scheme was also developed and experimentally validated using the SSPC to create artificial current and voltage stimuli.
69

An integrated opto-fluidic effector for aerospace applications

Berrill, Mark Graham January 1998 (has links)
No description available.
70

Helicopter control law design using eigenstructure assignment

Griffin, Stuart James January 1997 (has links)
No description available.

Page generated in 0.0751 seconds